Research with humans has suggested that cardiac acceleration accompanies the "rejection" of noxious stimuli, (the "Defensive Response" or DR), while attention to stimuli results in deceleration (the "Orienting Response" or OR). Larger decelerations are related to faster responding in reaction time (RT) tasks, allegedly due to a cortical facilitating effect mediated by receptors in the carotid sinus. A cerebral event which may be the cortical representation of this facilitation is the "Contingent Negative Variation" (CNV). It is characterized by the development of a negative electrical potential at the vertex, during the interval between two related stimuli. Greater negativity is related to faster responding in simple RT tasks. One study has shown a positive correlation between cardiac deceleration and cortical negativity. Other studies, including this author's previous research, have suggested that the above relationships may not apply in complex stimulus situations. Cardiac OR's have been observed in response to unpleasant stimuli (phobic objects), where DR's might have been expected. This author found cortical positivity associated with cardiac orienting. Heart rate responses varied with the affective nature of the stimuli, and the usual relationships between heart rate, cortical potential and reaction time were not found. The proposed study deals with the following, broad issues: 1. Does the cardiac response differentiate complex, stimulus content? 2. Does cortical positivity reflect attention? 3. How do cardiac and cortical measures relate to reaction time using complex stimuli? 4. How do cardiac and cortical measures inter-relate. Subjects will be asked to view a series of unpleasant, neutral and pleasant color slides, while cardiac, cortical, and other related measures are recorded. For half of the subjects, slide offset will be the signal to respond in a reaction time task. Polygraph output will be recorded for computer analysis.